The invention is targeted more specifically, without being restricted thereto, to valves for bottles of gas of all kinds, such as propane, butane or the like. These valves generally seal by means of the stuffing box which surrounds the upper part of the rod connecting the operating wheel with the closure member. These valves can be removed by unscrewing the stuffing box and taking it out of the body of the valve. For this, the stuffing box of known valves has a polygonal head, for example a hexagonal head, which is readily accessible underneath the operating wheel using a conventional spanner. This accessibility for slackening off the stuffing box may, however, constitute a serious hazard when a non-specialist attempts to "have a go" when the valve is on the bottle and the bottle is not empty. What may, for example, happen is that, observing a slight leak, someone may attempt to remedy this by trying to tighten the stuffing box. In this case, a mistake in the direction of rotation, especially when the stuffing box has a left-hand thread, may become the cause of serious accidents.